INTRODUCTION: Malignant neoplasms are the cause of significant socio-economic losses of society, and therefore their early diagnosis, as well as the diagnosis of precancerous diseases and the identification of risk factors for their occurrence remain urgent tasks of medicine. AIM: To study the prevalence of precancerous and oncological diseases of the oral mucosa (OM) in workers of Ryazan State Instrument–Making Enterprise (RSIME). MATERIALS AND METHODS: In May–June 2022, 301 employees of RSIME aged from 19 to 74 years were examined for the first time. During the examination, a clinical dental check-up and autofluorescence stomatoscopy were performed. The results of the examination were recorded in a card for assessing the dental status of adults, approved by World Health Organization. RESULTS: After a preventive examination of the workers of RSIME, 30.6% of the examined patients were found to have diseases and pathological changes in the OM, 9.8% was diagnosed with leukoplakia. From the total number of examined patients: 25.9% have a sanitized mouth, 32.9% smoke, and the most of smokers are people from 19 to 44 years old. CONCLUSION: The data obtained confirm the expediency of regular periodic medical examinations using screening diagnostic methods.